At present, power lithium-ion batteries are increasingly widely applied to various devices, including automobiles, uninterruptible power supplies (UPSs), power energy storage, field electricity utilization, etc. The lithium-ion batteries become the mainstream of the present battery market due to the advantages of high capacity and small size. However, the lithium-ion batteries are prone to being sharply heated up under the abnormal conditions of short circuit, over-charging and the like, and serious accidents such as explosion, combustion and the like may happen in the absence of protection measures. Thus, the lithium-ion batteries must be forcibly provided with over-voltage, over-temperature and over-current protection devices. In other words, one of the main technical problems of replacing the traditional lead-acid batteries with secondary lithium-ion batteries is to install protection circuits for over-current, over-charging, over-discharging and the like for the secondary lithium-ion batteries, so as to ensure safe operation of the batteries.
In the application fields of mobile phones, electric tools and the like, dedicated circuits are mainly adopted for detecting relevant parameters of batteries at present such as voltage, charging/discharging current and the like. When these parameters exceed the limited values, the charging/discharging loops of the batteries are cut off by switching off such switching devices as relays, metal-oxide-semiconductor field-effect transistors (MOSFETs), insulated-gate bipolar transistors (IGBTs), and the like, and the batteries stop charging/discharging, so that safe operation of the batteries is ensured. Although switching off such switching devices as relays, MOSFETs and the like is flexible and quick, the overall reliability of systems is low due to the complexity of peripheral control and drive circuits; in addition, the semiconductor devices, such as MOSFETs, IGBTs and the like, have the problems of poor interference resistance, poor current impact resistance and the like; and the relays have the defects of slow operation, high drive current, huge size and the like.
Moreover, in the forming process of an existing lithium-ion battery pack, many control points are needed, and when power lithium-ion batteries are used in series and in parallel, the management is very complex, and the cost of a protection system in a battery pack system always constitutes more than half of the overall cost. On the other hand, the present electronic semiconductor switches (e.g. MOSFETs) have the defects of short service life, poor stability, poor heat resistance, weak interference resistance, weak high voltage resistance and the like.
A certain number of battery cores must be connected in series and in parallel to achieve the required voltage and capacity in the application fields of electric tools, electric bicycles, small energy storage and the like, but the defects of the above switching devices such as relays, MOSFETs, IGBTs and the like greatly limit the application of the battery cores in these fields.
Therefore, it is extremely important to design and manufacture a controllable switch assembly which is simple in peripheral control circuit and stable and reliable in operation, has over-current resistance and can be connected in series and in parallel within a certain range in the application fields of electric tools, electric bicycles, small energy storage and the like.